Fe3O4 thin films are prepared by reactive sputtering and their magnetic, electric, and noise absorbing properties are investigated with the aim of thin film noise absorbers in gigahertz frequencies. Fe3O4 thin films were deposited on the glass substrate by reactive sputtering. It is found that the precise control of the oxygen partial pressure is the most critical to obtain the single-phase Fe3O4 thin film. The vibrating sample magnetometer measurement indicates that the saturation magnetization is 400 emu/cm3 and the coercive force is about 200 Oe. A microstrip line (with a characteristic impedance of 50 Ω) was used for the measurement of noise attenuation. Attaching the thin film on the microstrip line, the S11 parameter is increased from -60 dB (without a film) to about -15 dB (with a film). The S21 parameter is reduced to about -3 dB (about 50% in power) in the frequency range of 1–6 GHz, which is due to the magnetic loss of the Fe3O4 films. Power absorption (defined by the ratio of power loss to input power) increases with frequency and saturates to maximum value (about 0.5) in the frequency region of 4–6 GHz. It can thus be suggested that the Fe3O4 thin film is one of the hig- h potential materials for noise suppressors in gigahertz frequencies.